Control system



2 SheetS-Sheet l J. A. MULLER ET AL CONTROL SYSTEM Filed Aug. 21, 1942 Mai-ch 5, 1946.

INVENTORS J'OHAN A. MULLER,

BY -Howm E MMMLuN ATroRNEYs March 5, 1946. 1. A. MULLER ET A L 3 9 CONTROL SYSTEM Filed Aug. 21, 1942 2 Sheets-Sheet 2 II&

. lNVENTORS daum A. Muuu,

AT TORNEY Patented Mar. 5, 1946 I CONTROL SYSTEM Johan A. Muller. Dayton. and Howard F. MacMlllin, Mount Gilead, Ohio, assignors to The Hydraulic Development Corporation, Inc., Wilmington, Del., a corpo-ation of Delaware Application August 21, 1942, Serial No. 455,676

4 Claims.

This invention relates' to control systems and, in particular, to control systems for hydraulic circuits.

It is well known that when a hydraulic'press stands idle for a relatively long period of time. the press ram gradually slides or creeps downwardly due to leakage around hydraulically operable drivin'g means operatively connected with the press ram. When then the press is to be put into operation, the ram has first to be returned to its retracted or starting position. In case the driv- .ing fluid is supplied by a pump of the variable delivery type, it is customary, to positively connect the said pump with an electric motor for driving the pump, so that when the electric motor is started, also the pump is started, while substantially simultaneously the pump is automatically moved into return stroke position, if it does not already occupy the said return stroke position.

Similarly, when the driving fluid is supplied by a pump of the constant delivery type, it is customary, for various reasons, to positively connect the pump with the electric driving motor therefor, so that also in this instanc'e the pump starts delivering pressure fluid to the retracting means for the press ram immediately the electric driving motor is started.

Since, under these circumstances, the electric motor has to start under full load when. after a i relatively long period of idleness of the press, the

ram has to be returned to its retracted or starting position, special starter means is required to protect the electric motor. Furthermore, the power required for this Initial or conditioning operation is relatively high. A

It is, therefore, an object of this invention to provide a control system which may be used in connection With hydraulic presse-s for remedying the above mentioned drawbacks.

It is another object to provide a 'hydraulic system including a fluid operable plunger and pressure fluid means, driven by and connected to a motor, for supplying pressure fluid to the said plunger, in which the moto and thereby also said pressure fluid means may be brought up to full speed before said pressure fluid means delivers 'pressure fluid to actuating means for said plunger,

to thereby bring about a movement of the said plunger from an intermediate position to one of its end'positions.

It is a further object to provide a. contro system including a variable delivery pump having its shaft rigidly connected to the driving shaft of a. prime mover, in which electrically controlled means is adapted to hold the pump in substantially neutral or no delivery position while the' prime mover is being brought up to a desired speed.

Still another object of the invention consists in the provision of a control system including a variable delivery pump having its shaft rigidly y connected to the driving shaft of a prime mover,

in which hydraulically controlled means is adapted to hold the pump in substantially neutral or no delivery position while the prime mover is being brought up to adesired speed.

It is also an object of the invention to provide a control system which may be used in connection with a reciprocable plunger adapted to bring about a reduction in the speed of movement of said plunger at any desired point of its travel in one direction.

It is still another object of the invention to pro vide a control system for use in connection with hydraulic systems including a 'fluid operable plunger, a variable delivery pump for supplying pressure fluid to said plunger and a. prim mover rigidly connected to said pump, in which the pump linkage is at all time actuated without a sudden shock. p

A still further object of the invention consists in the provision of acontrol system including a fluid operable plunger and a constant delivery pump having its shaft rigidly connected to the driving shaft of a prime mover and adapted to supply pressure fluid to said plunger, in which control means is provided adapted to prevent said pump from delivering actuating fluid to said plunger before said prime mover has reached a predetermined speed.

These and other objects and advantages of the invention will appear more clearly from the following speciflcation in connection with the ac v companying drawings, in which:

Figure 1 diagrammatically illustrates a control system according to the invention in connection with a hydraulic press. v

Figure 2 shows a variation of the control system according to the invention.

Figure 3 shows a further embodiment of the invention in connection' with an open circuit.

General arrangement pump and, when moved into a second position, causes the pump to move into substantially neutral or no delivery position. The thrusters may be controlled in any convenient manner. -for instance, electrically or hydraulically.

when the system according to the invention is used in connection with a hydraulicepress and the press ram. after a relatively long period of idleness, is to be returned i'rom a position intermediate its end positions to its initial or starting position, the second mentioned thruster is moved into its second position, thereby moving or holding the pump in neutral position, while the prime mover tor the pump and. thereby. the pump, is brought up to a desired speed. When this speed has been reached, both thrusters are deenergized whereby the second thruster is made ineflective, while the return mechanism for the first thruster actuates the pump into its return stroke position. The plunger will then, without causing undue load upon the motor and the pump, be returned to its Initial or retracted position. The press may then be operated in the conventional manner.

When it is required, at a desired point of travel of the press ram in one direction, to slow down the movement of the ram, limit switch means is actuated. which. causes the second thruster to move into its first position.

Structural arraaement Reierringnow to the drawings in detail, the press system shown in Figure 1 comprises a press cylinder I having reciprocably mounted therein a press ram, generally designated 2, including a piston 3 and piston rods 4, 5.

connected to the piston rod 4 is a platen 6 with a platen arm 1, which latter is adapted to cooperat with a collar 8 adjustably mounted on a push rod 9. The push rod s is guided on the press frame in any conventiona manner, not shown in the drawings.

Also adjustably connected to the push rod a is a collar o for cooperation with an arm ll of a three arm lever, generaly designated l2. The arm li carries a pin |3 extending into a slot |4 oi' a control or thruster rod 15. The control or thruster rod 15 has adjustably connected thereto an abutment !6 engaged by the upper end of a spring l'l, the lower end of which engages a por- -tion !8 connected to a stationary member which may, for instance, be the press frame. The rod li has also adjustably connected thereto a collar s for abutment with the portion 18.

The lower end of the control or thruster rod I s is pivotally connected to an element 20 pertaining to an electrically controlled thruster 2l. The thruster 2| may be of any conventiona design, i ir instance, ot the type disclosed in U. s. Patent 1,947,241.

[I'he adjustable abutment 16 has connected ereto an arm 22 with an inclined end surface 23 ich is adapted to cooperate with a similarly aped rod 24. The rod 24 has adjustably mountthereon an abutment 25 engaged by one end of 'spring 25, while the other end of this spring 'gages a stationary element 21. The rod 24 also rries, adjustably mounted thereon, a colar 28 'apted to abut the stationary element 2'. The

:1 24 has connected thereto an armature 29 conjlled by a solenoid 30. The arrangement is such at when the rod 24 occupies its outermost right nd position with regard to Figura 1, it will ense and stop the arm 22 when the atter moves vnwardly from the position shown in Figure 1.

The three arm lever |2 is shiftable about a srecno-n pivot :I and has its arm 32 pivotally connected to a control or thruster rod 83. which latter is pivotally connected to an element 34 pertaining to the electrically controlled thruster il, which may be of the same type as the thruster 2| but has less power than the letter. The right hand end oi' the arm 32 has connected thereto one end of a spring ti. the other end of which is connected to a stationary element 31. The thruster :I has connected thereto a line s adapted, by closure of the switch ss, to -be electricalLv connected with the line 40 which, in its turn, is adapted, by ciosure of the switch 4l. to be connected with the line 42. The line 42 is connected to a line 43, one end ot which leads to the solenoid u, whereas the other .end is adapted, by closure oi' the switch 44, to be connected with a line 45, which latter leads to the line 38. Closure o! the switch 44 also establishes electric connection between a line 44 leading to the main supply line 41 with a line 48 leading to the thruster 2 l The thruster 2| has also connected thereto a line 49 leading to a line 50. one end of which is connected to the solenoid 35. whereas the other end of the line 50 is connected to the main supply line Bl. The thruster 2l has also connected thereto a line 52 adapted by closure of the switch 53. to be connected with the line 54. The line 54 is connected to the line 40, which leads to the main suppiy line 41.

The third arm 55 of the three arm lever l2 is pivotally connected to a link 56, which is pivotally connected to a flow control rod 51, pertaini ing to a variable delivery pump, enerally designated 58, and provided with a servomotor 59. The pump 58 is adapted to be driven by a prime mover 60, such as an electric motor.

The pump 58 has associated therewith a pilot pump SI. The pumps '58 and si are driven by one and the same shai't and may be arranged in the manner disclosed in the Ernst Patent No. 2,168,669.

The pump 58 is preferably oi' the type shown in the Ernst Patent No. 2,184,665, in which fluid from.the pilot pump is adapted to Shift the flow -control member of the pump selectively into forward or return stroke position. Furthermore, centering springs, not shown,in the drawings, are provided in a manner similar to that disclosed in the said Ernst Patent No. 2,184,665, which tend to hold the pump in neutral or no delivery position. From the above, it will be clear that when the prime mover to is started, also the pumps 58 and Bl are started. The pump i! has hydraulic connections 62 and 63 respectively leading to the upper and lower portion oi' the press cylinder i.

Referring to Figure 2, the control mechanisn shown therein diflers from that of Figure 1 merely in that the electric control o! the thrusters 2I and 35 and the solenoid 30 are replaced by hydraulically operable cylinder-piston-assemblies 64, 65 and 66. since otherwise the structure fully corresponds to that of Figure 1, the elements of Figure 2, corresponding to similar elements in Figure 1, have been designated with the same reference numerals, however, with the addition-al letter a.

operation It may be assumed that all parts of .the system described above occupy the position shown in Figure 1, with the exception that the press pisten 3 occupies a position intermediate its uppermost and lowermost positions. It may furthermore from the upper portion of the cylinder I by the pump 58. consequently, the ram 2 now moves upwardly. When the ram, during this upward movement, 'approaches the position shown in In hydraulic press systems heretofore known,

the starting of the pilot pump 8! would immediately cause fluid delivered thereby to shift the pump 58 into retraction stroke position, so that the prime mover 60, which as a rule is an electric motor, would have to be started under full load. This made the provision of special Starter means necessary to protect the said motor, while simultaneously causing a high surge of current.

However, according to the .present invention, the operator, either before or simultaneously with the starting of the prime mover 68, closes the switch 44, thereby causing current from the main supply lines 41 and l to energize the solenoid 38 and the thrusters 2l and 35.

Energization of the solenoid 30 brings about a leftward movement of the rod 24 so as to move the latter out of the path of' the arm 22.

Energization of the thruster 35 tends to bring` about a downward movement of the control or thruster rod 33. However, this tendency is overcome by the energization of the thruster 2 l, which is stronger than the thruster 35 and causes a downward movement of the thruster rod !5, so that the upper end of the slot I4 engages the pin I3 and positively holds the arm |.l of the three arm lever |2 in the position shown in Figure 1, at which position the collar 10 abuts the top of' the thruster 85. In this position, the flow control rod 51 causes the pump 58 to occupy its neutral or no delivery position.

Therefore, when now the prime mover 80 started and, thereby, also the pumps 58 and 61, pressure fluid delivered by the pilot pump Bl cannot cause shifting movement of the pump 58 to its retracted position, and is, therefore, bypassed, for instance, through a relief valve of any desired type to an exhaust in a conventional manner.

When the prime mover 60 has reached its desired speed, the pump 58 may be shifted into its return stroke position to bring about the full retraction o'f the press piston 3. To this end, the operator opens the switch 44, thereby deenergizing the solenoid 30 and thrusters ZI and 35.

The solenoid 30 has associated therewith retarding means, for instance a dashpot (not shown), which prevents the return of the rod 24 into the position shown in Figure 1 before the spring l'l has moved the rod l5 intothe position shown in Figure 1.

The spring 36 will then actuate the three arm lever l2 so as to bring about leftward movement of the flow control rod 51, whereupon pressure fluid delivered -by the pilot pump Bl moves the pump 58 into its retraction stroke position. Since, at this time, both the prime mover 58 and the pump 58 are at full speed, movement of the pump 58 into its retracted stroke position is carried 'out smoothly without undue load on the -prime mover 68.

- the lower portionof the press cylinder I.

Figure 1, the platen arm 'I engages the collar 8 and lifts the push rod 9 so that the collar !8 engags'the left end of the lever arm ll so as' to move the lever l2 in clockwise direction. When the ram 2 has reached the position shown in Figure l, the lever |2 is likewise in the position of Figure 1, in which position it has caused the flow control rod 51 to bring about movement of the pump 58 into its neutral or no delivery'position. As a result thereof, the press ram is halted in the position shown in Figure l.

In order to start a pressing cycle of the press ram, the operator closes the switch 39, thereby establishing electric connection between the lines 48 and 38, and energizing the thruster 35. As a result thereof, the three arm lever l2. is shifted in clockwise direction into a position in which the pin !3, carried by the lever arm ll, a'buts the upper end of the slot l4 on the rod |5 when the latter occupies the position of Figura l. This shifting movement of the lever |2 causes 51, as a result of which the pump 58 moves into full stroke forward position. Pressure fluid de- V portion of the press cylinder I. consequently,

the press ram 2 now moves downwardly.

When the ram is about to approach its work piece engaging position, 'it is desirable to slow down the movement of the press ram. To carry out such slow down operation, the operator closes the switch 53, thereby energizing the `solenoid 2l. As a result thereof, the thruster rod |5 moves downwardly until its arm 22 engages 'the rod 24, at which time the rod l5 comes to a halt. This downward movement of the thruster rod |5 causes a leftward movement of the lever [2, thereby moving the flow control rod 51 toward the p left so that the pump 58 moves to a restricted delivery position. consequently, a smaller quantity of pressure fluid than before is supplied from the pump 58 through conduit 82 to the upper portion of the press cylinder l and a corresponding amount of pressure fluid is withdrawn from The press ram 2 now moves downwardly at a reduced speed. Should it be desired to halt the press ram, the switch 4| may also be closed thus withdrawing the rod 24 from the path ofthe arm 22,

When it is desired to again speed up the movement of the ram, the operator again opens the switch 53 so that the thruster 35, which is still energized, shifts the three arm lever !2 in clockwise direction and causes the pump 58 to again move into full delivery forward stroke position. The ram 2 now gets the full delivery of the pump 58 and, consequently, again advances at high speed.

When the pressing operation has been completed, the operator opens the switch 39, thereby deenergizing the thruster 35 and enabling the spring 36 to impart rotation in anticlockwise direction upon the three arm lever !2. This causes a rightward movement of the flow control rod i 51 and, as a result thereof, the pump 58 moves into its full delivery retraction stroke position. Pressure fluid is then delivered by the pump 58 through the conduit 63 into the lower part of the press cylinder l, while fluid is withdrawn from the upper part of the press cylinder l through the conduit u. The press ram 2, theretore, moves upwardly.

When the press ram 2 approaches the position shown in Figura 1, the platen arm s, through the intervention o! the push rod l. lever !2, line 58 and flow control rod l'l, moves the pump I& to neutral or no delivery position, in the manner described above.

When the press ram 2 'has reached the position shown in Flgure 1, it comes to a halt. and the press is now ready for a new cycle.

If the solenoid 30 and the thrusters !I and Il are replaced by the cylinder-piston-assemblies -64, 65 and 60, it will be clear that the ram 2 may be operated in exactly the same manner as described above. The only diflerence in this instance consists in that the actuation oi' the rods na, lsa and :sa against the thrust oi their respective spring na, l'la and !sa will be brought about by supplying pressure fluid through the conduits 61, 68 and 69 respectively. The supply of fluid to and withdrawal oi' fluid from the cylinder-piston-assemblies N, 65 and 88 may be controlled by four-way valves of any conventional type.

While the control system according to the invention has been described in connection with a reversible variable delivery pump, it is understood that the invention is by no means limited to the use o such pump. It will be obvious that the control system according to the invention may also be used in connection with a one-way variable delivery pump and a !our-way valve of conventional design which, in addition to its two service positions, has at least a third position, namely, a neutral or closing position. The valve member will, in such an instance, be connected to the link 58 so as to be controlled thereby in such a manner that in one of its service positions the valve will admit fluid from the one-way delivery pump to one or the other end o! the press cylinder I, whereas, in its neutral position, it will prevent the flow of fluid to and from the press cylinder I. The delivery of the one-way pump will then be by-passed through a relief valve in the usual manner.

The slowdown effect can be obtained by moving the valve into a throttling position, so that only part of the respective service port of the valve is open.

Referring now to Figure 3, the structure shown therein corresponds in general to that of Figura 1, with the exception that the closed hydraulic circuit of Figure 1 has been replaced by an open circuit. ,More specifically, the variable delivery pump 58 of Figure 1 has been replaced by a constant delivery pump ll, which has its shaft rigidly connected with the driving shaft of the electric motor BGb. The pump 'H has one end connected through a conduit 12 with a tank or fluid reservoir 13, whereas the pressure side of the pump 'H is connected through a conduit 'N to a four-way valve 15. The valve 15 comprises a valve member 18 connected by a linkage 11 with the three arm lever I2b, which is controlled in a manner similar to that of lever |2.

Branchlng off from the conduit 14 is a conduit 18 including an electrically controlled normally closed shutoil' valve 19 and leading to the tank 13. The shutoii valve 19 may be by-passed by a pressure relief valve 80. The electric control for the valve 'IS is arranged in parallel with regard to the solenoid sob. Furthermore, a check valve 83 is arranged in the conduit 14 between the pump 'II and the valve 'IE so as to prevent &895374 I the ram Gb !rom dropplng when the pump is being by-passed through valve 19. The remaining parte correspond to those oi' Figure 1 and carry the same reference numerals as in Figura 1, however, with the additional letter b.

It may now be assuned 'that the press has been standing idle and that the ram Gb occupies a position intermediate its end positions. V is now desired to return the ram ob to its retracted position tor starting a pressing cycle, the operator starts the prime mover !ob and, simultaneously therewith or before, energizes the solenoid sob, the shutofl valve 18 and the thrusters !lb and 35b. In a manner similar to that described in connection with Figure 1. the lever izb moves into its neutral position, thereby shiiting the valve member 18 through the intervention of linkage 'll into its neutral position in which the flow of fluid through conduits szb and Bab is blocked. consequently, since the pump 'll was started simultaneously with the prime mover Bob, and since, due to the energization of the electric part oi the valve 19, this valve is open. the delivery o! the pump ll is by-passed to the tank 13.

When the prime mover Bob' has been brought up to the desired speed, the operator deenergizes the solenoid 3Ilb, the valve s and the thrusters zlb and aib, so that the spring :Gb shiits the lever l2b in anti-clockwise direction This results in an upward movement oi the valve member s so that, since valve 19 is now closed, pressure fluid from pump TI passes through conduit b into the lower part of the press cylinder lb, while fluid from the upper part of cylinder lb, flows through conduit 82b and conduits Bl and 82 into the tank 13; The ram Gb, therefore, moves upwardly. y

When the ram approaches the end of its re: traction stroke, the lever l2b is returned to its neutral position, in the manner described in connection with Figure 1. Thereiore, also valve member 16 returns to the position shown in Figure 3 and the delivery of pump 'H is by-passed through the reliei' valve 80 into the tank 13. The press now comes to a halt and is ready i'or a pressing cycle. The pressing cycle itself is performed in a manner similar to that described in connection with Figure 1, the only difl'erence consists in that the valve member 18 is controlled instead of the flow control member oi the variable delivery pump 53.

It will be understood that we desire to comprehend within our invention such modiflcations as come within the scope of the claim.

Having thus iuIly described our invention. what we claim as new and desire to secure by Letters Patent is:

l. The combination of a varia'ble delivery pump, electric motor means having its driving shatt positively connected with the driving shaft oi said pump, yielding means continously urging said pump toward full stroke position in one direction, opposed electricai thrusters for varying the delivery of said pump. and switch means seiectively operable simultaneously to energize both oi said thrusters to move and hold said pump in substantially neutral or no delivery position at any time said motor is being started.

2. The combination of a variable delivery pump, electric motor means having its driving shatt positively connected with the driving shait oi said pump, yielding means continuously urging said pump toward full stroke ''ition in one direction, a first electrical-thruster operable to move said pump against the thrust of sai-d yieiding means into said full stroke position in the other direction, a second eiectricai thruster operable to move said pump into neutral or zero stroke position against the thrust of said first thruster, first switch means for energizing both of said thrusters simuitaneously for positioning said pump in neutral at any time said motor is being started, and second switch means selectively operable !or energizing said thrusters independently.

3. The combination of a variable delivery pump, electric motor means having its driving shaft positively connected with the driving shaft of said pump, a first eiectrical thruster operabie to move said pump into full stroke position in one direction, a second electrica thruster opera-ble to move said pump against the thrust of said first thruster into substantialiy no delivery position, a stop selectively positionable to stop said second thruster in order to position said pump in reduced stroke position, switch means selectiveiy operable for energizing both of said thrusters simultaneously !or positioning said pump in neutral when said motor is ibeing started, or tor energizing said first thruster independently, or for energizing said second thruster independently, and .means selectively operable for rendering said stop effective or ineffective.

4. The combination of a variable deiivery pump, electric motor means having its driving shaft positiveiy connected with the driving shaft of tor positioning said pump in neutral, and other switch means seiectively operable for energizing said first and second thrusters independently for moving said pump, respectiveiy, into full stroke or reduced stroke position in said one direction.

JOHAN A. MULLER. HOWARD F. MACMILLIN. 

